The highway transportation system in North America is almost totally dependent on fossil fuels, and the quantities consumed are staggering. Long haul semi-trailer trucks alone consume about 16 billion gallons of Diesel fuel per year. In addition to the direct economic costs, the indirect costs include air and water pollution, and depletion of energy resources.
For highway vehicles cruising at typical highway speeds on level roads, aerodynamic drag accounts for the largest engine load, and typically consumes a little over twice the power consumed by rolling resistance. Any significant reduction in aerodynamic drag translates directly into reduced fuel consumption, with the percentage fuel savings typically falling in the vicinity of two thirds of the total aerodynamic drag reduction.
The need for and benefits of reducing the aerodynamic drag of highway vehicles are so obvious, so compelling, and so widely recognized, that this goal often assumes the status of a hidden assumption. It therefore logically follows that all methods, or likely combinations of methods, known to those skilled in the art of aerodynamics of highway vehicles, should already be well researched and the results well documented.
Because large trucks continue to be designed and built with maximum cargo capacity and ease of loading as their primary goals, it is important for any new aerodynamic devices to be designed and built as add-on devices which are easily installed on both new and existing truck bodies, as currently manufactured.